Here's a literal definition of a "Physical" Network Model: When you're working on wiring in a networking lab with hundreds of wired connections and have bits and pieces left over. You then use the remains to create stuff. And either sell them or leave them there for others to see.
Tips: When dealing with a bunch of Ethernet wires, best to label each wire and test them before mounting them on a rack - If you don't do this and something goes wrong you're gonna have a bad time.
Design: This would normally fall under the 'Designed' category, but I didn't make it. Credit this to P. Miller and V. Tachkov instead.